After missing its official onset date of June 1, Southwest Monsoon finally arrived in Kerala on June 5. While it is important to understand why onset of Monsoon in India was delayed, it must be noted that onset date is inconsequential to overall Monsoon performance.
The normal date for onset of Monsoon in India is June 1. But this is just an average date which has been worked out over the years. Variation in the actual onset date is completely normal. You simply cannot expect Monsoon to make onset on June 1 every year. This is because variance in onset date is a built-in characteristic of Southwest Monsoon.
For example, onset date of Monsoon in 2014 was June 6. In 2013, the onset date was June 1 and in 2012 the onset date was June 5. Back in 2011, Monsoon made an onset in India on May 29. Whereas, in the year 2009, Monsoon arrived in India as early as on May 23. Thus, the actual date of onset of Monsoon varies from year to year.
When we compare the amount of rainfall received in the month of June over the years, things become clearer. Here’s a look at amount of rainfall received in the month of June in the last few years.
While the normal onset date is an important date giving us a fair idea about the arrival of Southwest Monsoon, it cannot be used as a tool to determine overall Monsoon performance. What really matters is how Monsoon systems are behaving. The frequency and track of Monsoon systems is the key to rainfall distribution over various parts of the country. To sum it up, rainfall pattern and Monsoon performance are largely independent of the onset date and are affected by other factors like behavior of weather systems in the Arabian Sea and Bay of Bengal.
(Featured Image Credit: thehindu.com)